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Flashcards in Corneal Function Deck (39)
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1

What are the primary functions of the cornea?

-refract light
-transmit light
-protects the internal parts of the eye
---fast healing
---minimize infection
---avoid injury/damage

2

What are the factors that affect refraction?

-curvature of the anterior surface
-curvature of the posterior surface
-corneal thickness
-change in refractive index from air to cornea
-change in refractive index from cornea to aqueous

3

What is the total power of the eye?

~60D

4

What is the power of the cornea?

~40-48D

5

The cornea is __ the power of the eye

2/3 to 3/4

6

We want ___scattering, _____ distortion, and ___ transmission

-decreased scattering
-minimal distortion
-maximal transmission

7

What are the 5 keys to maximize light transmission?

-smooth optical surface
-regular surface of epithelial cells
-absence of blood vessels
-correct spatial arrangement of collagen fibrils in the stroma
-less than 1% light scatter

8

T/F: the cornea is one of the most sensitive tissues in the body

True

9

Where is the cornea most densely innervated?

The center

10

What nerve supplies the cornea?

Ophthalmic division of the trigeminal nerve

11

What is the normal CV of endothelium?

0.25

12

What shape of endothelial cells?

Hexagonal

13

T/F: endothelial cells grow back

False. Once they are gone, they are gone

14

The stroma makes up ___%of the cornea

90%

15

What is the regular size of collagen fibrils and the spacing?

And why is this important

Size: 300A
Spacing: 550A

Important for corneal transparency

16

The corneal transparency is optimal when the stroma is ____ water

75%-80%

17

Tough layer of collagen and laminin that protects the underlying layers

Bowmans layer

18

In PRK what layer do you destroy?

Bowmans layer

19

What type of junctions does corneal epithelium have?

Tight junctions

20

This layer has anionic proteoglycans that pull water in

Stroma

21

This layer of the cornea slowly leaks fluid into the cornea

Endothelium

22

Corneal hydration is dependent on?

-barrier function of epithelium and endothelium
-anionic characteristics
-water and ion transport

23

What are the major driving forces or water transport across epithelium and endothelium?

Cl- extrusion and Na absorption

24

Small integral membrane proteins residing in the plasma membrane

Aquaporins

25

What are some roles of aquaporins?

-channels
-cellular processes
-cel migration

26

What does high IOP do to water?

It can move excessive water into the stroma from the anterior chamber and overwhelm the endothelial transport system

27

A minor abrasion of the epithelium causes the loss of?

Zonular occludens

28

What are 2 results of a corneal abrasion?

-edema
-haziness

29

What does an epithelial edema do to VA?

Decreases VA

30

When do corneal abrasion often heal?

24-48 hours